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수치 해석 방법을 이용한 크리프 균열 진전에 미치는 1차 크리프 속도의 영향 평가 : 1차 크리프 속도를 고려한 크리프 균열 진전의 유한요소
최현창 동명정보대학교 1999 東明情報大學校論文集 Vol.2 No.-
An elastic-viscoplastic finite element analysis is performed to investigate detailed growth behavior of creep cracks and the numerical results are compared with experimental results. In Cr-Mo steel stress fields obtained from the crack growth method by mesh translation were compared with both cases the secondary creep rate is only used as creep material property and the primary creep rate is included. Analytical stress fields, Riedel-Rice(RR) field, Hart-Hui-Riedel(HR) field and Prime(named in here) field, and the results obtained by numerical method were evaluated in details. Time vs. Stress at crack tip was showed and crack tip stress fields were plotted. These results were compared with analytical stress fields. There is no difference of stress distribution at remote region between the case of 1st creep rate + 2nd creep rate and the case of 2nd creep rate only. In case of slow velocity of crack growth, the effect of 1st creep rate is larger than the one of fast crack growth rate. Stress fields at crack tip region are, in order, Prime field, HR field and RR field from crack tip.
장기운영 항공기 주익 구조물 피로임계부위의 손상허용평가
천영철(Young-Cheol Chun),김원철(Won-Cheol Kim),진지원(Ji-Won Jin),정태진(Tae-Jin Chung),강기원(Ki-Weon Kang) 대한기계학회 2017 大韓機械學會論文集A Vol.41 No.2
본 연구의 목적은 항공기 주익 구조물에 대한 피로균열진전 해석 및 실험을 통하여 운영 기간에 따른 장기 운영 항공기의 손상허용성을 평가하는 하는 것이다. 이를 위하여 주익 구조물의 피로임계부위 2 곳을 대상으로, 선행 연구에서 개발된 알고리즘을 기반으로 산출된 피로응력 스펙트럼 및 상용 코드인 NASGRO 를 이용한 피로균열진전해석을 수행하고 그 결과를 참고문헌의 결과와 비교하여 피로응력 스펙트럼 및 균열진전해석방법의 타당성을 확인하였다. 또한 실제 주익 구조물에서 채취한 시험편 및 이와 동일 재료로 가공된 시험편을 대상으로 위의 피로응력 스펙트럼을 적용한 피로균열진전시험을 실시하고 그 결과를 이용하여 운영 기간에 따른 주익 구조물의 손상허용성을 평가하였다. This study aims to assess the damage tolerance of the wing structure of aged aircraft with long-term service through the fatigue crack growth analysis and tests. For the fatigue-critical locations (FCL) W2 and W4 in the wing structure, the fatigue stress spectrum was derived based on a previous study. Thereafter, a crack propagation analysis for the FCLs was conducted using the commercial software NASGRO<SUP>TM</SUP>. The algorithm for the fatigue stress spectrum was verified. Fatigue crack growth tests were then performed for two types of specimens: Type #1 was extracted from the wing structure of aged aircraft, and Type #2 was made of the same material as the wing structure. By comparing the experimental results of these specimens, we assessed the damage tolerance of the wing structure of aged aircraft with service time.